Look for: Trumpet, sheath, and modified A-line gowns. Find a style with a waistline above your natural waist, to make the lower half of the dress (and therefore you) appear longer. The fabric is up to you―you can pull off a high sheen. But the detailing should be small (no huge bows) and limited to the bodice, to draw the eye upward.
Keep in mind: Be wary of dresses with a dropped waist, which will make your legs seem nonexistent, and ball gowns―it's easy to get lost in that voluminous skirt. Also, avoid anything calf-length, which will make your legs look short.